New to this thread after lurking...

This is great...lots of interesting comments and conversation from ones that now appear banned. What a roller coaster !!

Here is my experience...

Brand new in Sept 20 Kona FWD 1.6t 7DCT. Currently at 13,500 miles of mostly highway driving.

When I first got the car I did check the oil level, but has always seemed high. Even at final inspection at the dealer. Didn't think too much about it.

First oil change around 4,500. Took it to the dealer. Wasn't super pleased with the answers I asked about full/semi synthetic, weights, etc. Oh well. I put it on the service request so there is a "record." The oil level at 4,500 was about 3/16" higher on the dipstick than at delivery. Got it changed with what the receipt says as 5w-20. I asked the service person to clarify and they walked away for a few minutes and came back and said, "...yeah, the mechanic said he put in 5w-30..." Well, they may have just gone to the bathroom or took a 5 minute break and came back and told me that. Either way, I don't know. It just wasn't a "warm and fuzzy" feeling with that answer.

Around 8,000 I started noticing that the oil level was over 1/4" higher than at the 4,500 oil change. It also smelled of gasoline. I freaked because I was about to go on a lengthy trip....and have read too many horror stories on this board. Anyway, I got it changed at one of local mechanics and they actually had NAPA filters and Castrol 5w30 Dexos gen2. I figured It was OK for what I needed...right now. (The dealer here reduced their hours for COVID and went back to their pre-COVID hours and their booking system is all screwed up. So...the dealer could not change the oil within a month of 8,000 miles.)

Now, I have 13,500 miles on the car and just did another oil change...myself this time. The oil level raised ever so slightly over this 4,500 mile oil, but no where near it did with the dealer oil change at 4,500. This has sold me on making sure I know what goes into that car. I'm kinda depressed as I do get "free" oil changes from the dealer for 100,000 miles...now I'm paying for them.

There is one major change I did to my driving "style" at the 8,000 mile change. I started to use Sport Mode exclusively. To be honest, if nothing else I prefer the Sport Mode throttle response to the "Eco" mode/non-sport mode. That alone is worth the other changes/benefits that come with it.

Before (factory oil and questionable dealer oil at 8,000) I just ran it in the default non-sport mode. It did everything I need. That is also when I noticed the most oil increase, especially with the questionable dealer oil change. Certainly not scientific.

Most of my driving is with cruise control on. 70mph Interstate (with a lot of hills), 35mps city for about 20% of total driving, lots of back country roads with 45mph speed limits.

Anyways...the point being is that in the default/non-sport mode, I never noticed how lazy the car was to downshift on hills. The turbo was probably going full-boil at 1900 to 2100 rpms. Starting with new oil at 8,000 miles, I put it in Sport Mode and would manually downshift using the Instantaneous MPG gauge as a replacement for a real vacuum/boost gauge. Under any sustained load like going up hills, when the Instantaneous Gauge would show less than 25 (half way bar graph), I would downshift. I figure a couple of hundred extra RPMs would allow the engine to breathe better and be able to handle the constant turbo boost limiting any pre-ignition as well as not flooding the cylinders with extra fuel to cool it down.

Now... on some roads I drive they are very flat and straight. I can get the engine to about 1,800 RPM's with no real load and the fuel mileage goes through the roof. I guess is you think about the amount of boost a turbo can deliver at at specific RPM, you can "trick" your engine into amazing things. One thing is that this car is a brick. The aerodynamics leave a lot to be desired. The turbo is on almost the entire time at 70mph. The engine is a bit too small for a long legged highway cruiser, but it still does that well. If I drive at 50-60mph on flat roads, I can get about 40mpg.

These are some of life's mysteries...does a known specific full synthetic oil make that much of a difference with GDI oil dilution? Does just upping the RPM's keep the oil dilution at bay? I dunno...all I know to do is change the oil every 4-5k miles with a full synthetic that has some flashy "GDI Engine Approved" on the label as well as keep the RPM's up when under load.

This is part of the vague point I'm making about keeping your RPM's up when you are on the turbo. Don't get me wrong, Hyundai made a great car. Easy foot-down-horn-on drivability right off the showroom floor. The "problem" with this is with regular 87 octane gas, GDI, and mid-grade oil you will eventually run into long term problems.

tl;dr-- Change your oil with a high quality synthetic. Don't let the engine "labor." Downshift when the gauge gets below 35 instantaneous.

 

I got the same happening in my 2018 turbo.. dealership told me that the oil was over filled. It was getting into the turbo. Still at the shop.

 

im sure this is a bit late. But from my understanding the High Pressure Fuel Pump (HPFP) sits on top of the camshaft, giving it direct access to the top of the engine. If the pump fails, or begins to fail and leak fuel into the motor, this will cause your issue. It sounds like injector, hpfp, or the fuel sensor could be bad. Check engine would fire if sensor I believe, but a scan tool with bidirectional features should give you some data to work with. Start live data stream and drive it and see what the injectors look like at both ends. Test injectors with the tool and see if it activates them and what symptoms are present during accuation test. Lastly, test the power of the car. Does it idle rough? Does it lose power and if so, what speed did this occur at? Shaking of the car at idle when cold, warm and specific speed? These things need to be known also. Your TB would kick a code and check engine light, as the IAC and the MAF amongst others like o2 would be running rich/lean etc and would more than likely tell you something is up. Look for mechanical problems when no TDC and the more obvious dash lights are not warning you of anything. It's hard to find anyone that knows how to do their job anymore, let alone do it extremely well. Good luck. Don't buy specific cars from specific countries. I won't name them here!

oh and again forgive me on not being up to date with the Kona, but the 2017 Hyundai Elantra, Accent etc all seem to have a similar issue with carbon buildup due to GDI with no Port Injection flush on valves. Be sure to run highest octane you have available. Also make sure the PCV valve is replaced every 20k miles, oil is changed every 3k and your valves are cleaned with intake cleaner like seafoam every 20k miles. Also check to ensure the carbon buildup in the injectors and valves aren't gummed up with carbon. Will require walnut blasting at that point or manually cleanup. More than likely if the car is old like pushing 100k or higher, and has never had that done before, you're looking at a probably piston ring issue and that is expensive and labor intensive job. But get it fixed because fuel dilution causes seals to dry out and other catastrophic failure events to occur if left unfixed.